1. Field of the Invention
The present invention relates to a power conversion device in an electric vehicle wherein the device uses a short-circuit capacitor.
2. Description of Background Art
A DC/DC converter as a power conversion device used in an electric vehicle is described in Japanese Patent Application Publication No. 2006-33966 wherein an inductor is connected in series to a battery. Switching elements are connected in series to the inductor and a capacitor and a load are connected in parallel to the switching elements.
In a DC/DC converter where an electrolytic capacitor or a film which withstands high voltage is used between a positive power line and a negative power line, even when an excess voltage or the like is applied to the electrolytic capacitor or the film, the positive power line and the negative power line are never short-circuited because the circuit between the electrodes is open. However, being large in size and requiring high costs, the electrolytic capacitor or the film is not suitable for a small electric vehicle such as an electric motorcycle.
In contrast, a ceramic capacitor being small in size and having excellent ripple characteristics can be considered suitable for use in a small electric vehicle. However, in such a case, a voltage detector or the like needs to be additionally provided to detect a short circuit caused upon application of an excess voltage or the like, and this increases the number of components and thus increases the costs.